Field of the Invention
This invention relates to a styrenic resin composition for extrusion of sheets, films, pipes and profiles, more particularly to a composition of styrenic resin which is suitable for thermoforming extrusion products.
Conventionally, styrenic resin which contains grafted rubber particles, such as acrylonitrile-butadiene-styrene, methyl methacrylate-butadiene-styrene, acrylonitrile-methyl methacrylate-butadiene-styrene and acrylonitrile-EPDM-styrene are mainly used for injection molding and some of which are used for extrusion of sheets, films, pipes and profiles and further to thermoforming of the extrusion products.
The styrenic resins generally have some practical problems when they are used in the extrusion of sheets, films, pipes and profiles even if the same styrenic resins have no problems in the injection molding process. First, die lines and uneven gloss are formed on the surface of the extruded product, thus affecting the appearance of the extruded product. Second, the roller will be contaminated by oily material during the manufacturing process, thus interrupting the extruding process. Third, an injected product which is made of the styrenic resin has a sufficient impact strength, while the extruded product of sheets has a poor impact strength. When the extruded product of sheets and films is further treated by means of the thermoforming process, the thickness of the product is not uniform, thus resulting in poor appearance and strength.